A dissolved gas in a liquid may cause corrosion of tubes through which a liquid flows, decrease in heat exchanger effectiveness and pressure due to bubble generation, or uneven application of a liquid due to generated bubbles. Hence, depending on the method and purpose of using a liquid, degassing is required.
For instance, a separation membrane module (see FIG. 2) that is disclosed in JP2002-253936A (Reference 1) can be used for degassing a liquid (a liquid to be degassed). The separation membrane module 101 shown in FIG. 2 is provided with a tubular housing 102 and flanges 103 that seal the openings of the housing 102. In the separation membrane module 101, polytetrafluoroethylene (PTFE) porous tubes 109 are contained in the housing 102 as gas-permeable tubes. The respective ends of the PTFE porous tubes 109 are connected to an inlet (liquid inlet) 105 and an outlet (liquid outlet) 106 for the liquid to be degassed. In such a separation membrane module 101, a liquid to be degassed is allowed to enter from the liquid inlet 105 and to flow through the PTFE porous tubes 109, while the inside of the housing 102 is decompressed through a gas supply port 107 and/or a gas exhaust 108 formed in the housing 102. Thus the liquid can be degassed (as described in paragraph [0017] in Reference 1).
In the separation membrane module 101 disclosed in Reference 1, the housing 102 and the flanges 103 are joined to each other by a method such as welding, bonding, screwing, etc. (as described in paragraph [0018] in Reference 1). When they are joined to each other by welding, the property of sealing between the housing 102 and the flanges 103 is excellent. However, members contained in the housing 102, for example, the gas-permeable tubes may be damaged by the heat that is applied during welding. In the case of joining them to each other by bonding, an adhesive may be deteriorated by the substance that has permeated the gas-permeable tube in a gaseous state. This may cause the deterioration in the property of sealing between the housing 102 and each flange 103. In the case of joining them to each other by screwing, in order to maintain the property of sealing between the housing 102 and each flange 103, it is necessary to provide sealing members such as a seal tape, an O ring, a gland packing, etc. Furthermore, the use of a sealing member having chemical resistance to the liquid to be degassed may be required depending on the type of the above-mentioned liquid. However, suitable sealing members are unavailable or even if they are available, they are very expensive.